August 20, 2007—An unusual new star may shoot some holes in astronomers' theories.

Calvera, whose discovery was announced on August 20, may be the closest neutron star to Earth, at a mere 250 to 1,000 light-years away, scientists say. Neutron stars are ultradense, cold remnants formed when extremely large stars collapse after going supernova.

The find's name hails from the villain of the 1960 western The Magnificent Seven, since Calvera is now the eighth known "isolated" neutron star—meaning it was discovered without associated supernova debris, stars, or pulsating radio waves.

According to Robert Rutledge, lead author of a study on the star slated to appear in an issue of the Astrophysical Journal, the new find is rather mysterious.

"Either Calvera is an unusual example of a known type of neutron star, or it is some new type of neutron star, the first of its kind," he said in a press release, adding that its closeness and brightness make it a great candidate for further study.